Conventionally, among flow control valves such as those described above, bellows seal types and diaphragm types are known. The former, the bellows seal-type flow control valves, have a composition in which the gas flow rate is controlled by means of controlling the size of a gap between a valve aperture and a needle-shaped valve which is operated in accordance with the operation of a bellows. For this reason, the problem of contamination occurs as a result of the microparticles generated as a result of the friction between the needle-shaped valve and the inner walls. Furthermore, the degree of mechanical precision between the component elements, such as the valve aperture and the valve, exert a direct influence on the accuracy of gas flow rate control. As a result, in order to restrict undesirable variation in gas flow rate control, it is necessary to maintain an extremely high degree of accuracy in the machining of the component elements described above, and there is a problem in that productivity declines. Accordingly, in, for example, the case in which a highly pure special gas for semiconductor device manufacturing is handled, such a valve is inappropriate for use.
Furthermore, a conventional diaphragm-type flow control valve was disclosed in, for example, Japanese Utility Model Application, First Publication, No. Hei 1-128078. This diaphragm-type flow control valve was provided with a drive unit comprising a combination of a rack and pinion mechanism and an eccentric cam mechanism; as a result of the motion of the above-described rack, the above-described eccentric cam was caused to rotate, and furthermore, this rotation was transmitted to a diaphragm via operational elements such as upper and lower stems and the like, and the diaphragm was caused to move.
However, in the conventional diaphragm-type flow control valve described above, the composition of the drive unit included primarily the two mechanisms, the rack and pinion mechanism and the eccentric cam mechanism, described above. Furthermore, between these two mechanisms and the diaphragm, operational elements such as a lower stem, which moved in accordance with the diaphragm, or an upper stem, which was an element driven by the eccentric cam, or the like, were disposed. For this reason, the number of parts increased, and the production costs could not be reduced below a certain level. Furthermore, it was necessary to concomitantly provide both of the mechanisms described above in the drive unit which was coupled to the main unit. For this reason, the outward appearance was unavoidably poor, having an irregular shape. Moreover, there is a limit to the miniaturization of these two mechanisms, as a result of manufacturing technology which is based on constraints in the present material development technology, and there is thus a limit to the miniaturization of the apparatus as a whole.
On the other hand, the manually operated metal diaphragm valve which is used, for example, in a semiconductor manufacturing line or a refining line for ultra-pure fluid having an impurity concentration of 1 ppb or less, is provided with a handle for the purpose of manual rotation. This handle is coupled to the valve stem and rotates together with this valve stem. Furthermore, this valve stem is supported by a bonnet, which is connected to the valve casing, so as to be capable of reciprocating motion in the axial direction thereof, and so as to be capable of rotation about the axis thereof.
In the metal diaphragm valve described above, the rotational torque which is applied to the handle described above is converted into a thrust force along the axial direction of the valve stem, and by means of this, the diaphragm, which is linked to this valve stem, is pressed into the valve seat, and thereby, the desired cut-off force is obtained.
However, in this conventional metal diaphragm valve, the operational force placed on the handle by a human being is transmitted in an unchanged manner to the valve seat via the valve stem, so that there are cases in which excessive cut-off force is generated. Accordingly, an excessive compressive force is applied to the valve seat or the diaphragm, and as a result, there are occurrences of the deformation or damage of the valve seat or diaphragm, and as a result, there are cases in which the service life of the metal diaphragm valve is shortened.
A diaphragm valve 305 in which, as shown in FIG. 11, a conversion mechanism 304 for converting the rotation of a valve stem 303 into reciprocating motion in the axial direction was provided at the upper end portion of a bonnet 302 connected to the valve casing 301, was conventionally known as a metal diaphragm valve which was used in order to solve these types of problems. This conversion mechanism 304 is provided with a cylindrical cam member 306 which is attached to the outer circumference of the upper end portion of bonnet 302, a pin 307 which is affixed to the end of valve stem 303 projecting from bonnet 302, and a pair of ball bearings 308a and 308b which are attached to both ends of this pin 307. Furthermore, pin 307 penetrates valve stem 303 in a diametrical direction, and rotates together with this valve stem 303; the ball bearings 308a and 308b which are at both ends of this pin 307 have a structure in which they are in contact with the cam surface 309 at the upper end surface of cam member 306 while rolling thereon.
In the diaphragm valve 305 shown in FIG. 11, when an operator rotates valve stem 303 via handle 310, ball bearings 308a and 308b move along cam surface 309 in accordance with this, and by means of this motion, the valve stem 303 moves reciprocally in the axial direction thereof in accordance with the shape of the cam surface 309. Here, the stroke amount and lift characteristics of valve stem 303 are determined in accordance with the shape of cam surface 309.
However, the conversion mechanism 304 described above is attached to the upper end portion of bonnet 302, which is separated by a considerable distance from the valve seat within valve casing 301, so that in cases in which the lift amount of the valve stem 303 is small with respect to the rotational angle of handle 310, as is the case with a diaphragm valve 105 having a small diameter, there are cases in which undesirable variation is produced in the lift characteristics of the valve stem 303 as a result of the position at which cam member 306 is attached. For this reason, by adopting a configuration in which cam member 306 can be freely moved in the axial direction so as to screw onto the outer circumferential surface of the upper end portion of bonnet 302, the positioning and fastening of cam member 306 is conducted by means of a dedicated lock nut 311 which is screwed onto the outer circumferential surface of the upper end portion of bonnet 302.
Accordingly, in the diaphragm valve 305 containing this conventional conversion mechanism 304, cam member 306 and ball bearings 308a and 308b are present at the end portion of bonnet 302 on the side of handle 310. For this reason, this end portion of bonnet 302 has a disproportionately large shape in comparison with the valve casing 301 side.
Furthermore, in recent manually-operated metal diaphragm valves, it has come to be seen as important that an indicator which displays the degree of opening of the valve be provided. Indicators are known, for example, in which the degree of opening of the valve is indicated on the upper surface of the handle, and indicators in which the handle has a shape which is non-symmetrical with respect to the valve stem, and the degree of opening of the valve is determined from the position of the handle, and the like, are known. Here, indicators which operate according to the method in which the degree of opening of the valve is determined from the position of the handle are of no use in, for example, valve apparatuses which are provided with a plurality of connecting ports, such as in 3-way valves, or in valve apparatuses having complex shapes, such as block valves. Accordingly, in order to display the degree of opening of the valve irrespective of the type of valve apparatus, it is advantageous to employ a method in which an indicator is incorporated in the handle.
However, when an indicator is incorporated into a diaphragm valve 305 containing a conversion mechanism 304 such as that described above, a large conversion mechanism 304 is present in the diaphragm valve 305 at the end of the bonnet 302 which is on the side of handle 310. Accordingly, it is impossible to provide the space necessary to incorporate the indicator around handle 310. For this reason, the method in which the handle 310 has a shape which is non-symmetrical with respect to valve stem 303 must be adopted for the display of the degree of opening of the valve. Accordingly, depending on the type of valve, it is sometimes impossible to determine the degree of opening of the valve. Moreover, the conventional conversion mechanism 304 which is described above requires ball bearings 308a and 308b, which project outwardly in the diametrical direction from valve stem 303. For this reason, when a miniaturization of the entire valve apparatus is required, these ball bearings 308a and 308b present difficulties, and the incorporation of the conversion mechanism 304 becomes effectively impossible.
It is an object of the present invention to provide a diaphragm-type flow control valve which enables a simplification and miniaturization of the composition of the entire mechanism, and which allows for a reduction in manufacturing costs.
It is a further object of the present invention to provide a manual valve apparatus which is capable of easily and compactly incorporating an indicator displaying the degree of opening of the valve around the handle, even when a conversion mechanism which converts the rotation of the handle to reciprocal motion is provided, and moreover, which achieves a simple and miniaturized structure of this conversion mechanism and allows for the placement thereof within a guide member.
It is a further object of the present invention to provide a manual valve apparatus which enables a confirmation of the completion of the opening or closing operation of the valve not merely visually, but also by means of a sound or a vibration transmitted to the handle, so that by means of this, the opening and closing operation of the valve can be more reliably conducted, and which prevents undesired rotation of the valve stem or the handle even during use under conditions in which vibration is transmitted to the valve stem.